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Wednesday
Dec302015

Making a diagnosis of bacterial meningitis

 

 

 

 

 

 

 

 

 

 

What is the big deal?

As ED doctors, our first priority is to diagnose and treat life-threatening conditions.  Bacterial meningitis is one such example, where if missed, 21% patients die and many more suffer devastating complications.  Because we see so many of the "relatively well" patients who present earlier on, there is a huge potential for missing the diagnosis or mislabelling it as "viral meningitis".  A careful history can help weed out other causes of common benign conditions such as migraine or tension headache while maintaining a high index of suspicion for this infamous disease.  

 

How do you tell if someone needs an LP?

It is dangerously presumptive to call a meningitis viral without an LP result to back it up. It has been shown that clinical features alone cannot reliably differentiate between viral and bacterial meningitis when you have a well patient in front of you. This is the take home point : it is impossible to make a definitive diagnosis without a LP!  Referring a patient to short stay without an LP is not an acceptable practice in The Northern ED.

According to a study by Diederik et al (NEJM 2004), these are the frequencies of symptoms in a prospective cohort of patients with bacterial meningitis :

Rash present in 26%      }
Altered GCS 69%           }  this classic triad only present in 44%
Neck stiffness 83%        }
Headache 87%
Almost all present with at least 2 of the following fever, headache, neck stiffness and altered GCS

When is the best time to do an LP?

As soon as practicable is the answer!  Assuming there is no concern of raised intracranial pressure, an LP must take priority over other forms of investigation.  If a CTB-before-LP approach is taken, or if delays are expected, ensure the patient receives appropriate dose antibiotics and dexamethasone preferably after a single set of blood culture and within 1 hour of raising the clinical suspicion.  This should be the standard of care for ALL patients suspected to have bacterial or viral meningitis.  And always remember to get sufficient samples (10 - 15 drops for each tube is enough) and ask specifically for pneumococcal antigen and viral PCR studies. Antibiosis does not affect the pneumococcal antigen test (BINAX NOW) which yields extremely high at almost 100%.

 

So the patient is in SSU... what now?

Obviously supportive care is important.  If the LP comes back negative, the patient can be safely discharged with analgesia provided symptoms are improving with a note of caution : studies have shown 11 - 30% false negative result (!).  In particular, be suspicious of the immunocompromised, partially treated and where duration of illness is short.  If the LP is POSITIVE, one could categorise into several infective aetiologies but this is not always straightforward when the classic textbook descriptions are not all there, which is where the viral PCR or bacterial antigen test will help you here.  See table below courtesy of LITFL :  

 

 

To summarise, a careful clinical assessment alone is not sensitive enough to rule out bacterial meningitis but could indicate an alternative benign condition.  Nevertheless, all suspected cases must have a lumbar puncture and receive empiric treatment BEFORE admitting to the short stay unit.  A lumbar puncture is the gold standard for making a definitive diagnosis.  Most cases of viral meningitis respond to supportive care while confirmed or indeterminate cases will need specialist ID or Neuro input.

 

Tuesday
Nov242015

Teaching Nov 25

Tomorrow, we will have Caitlin Farmer, Physiotherapist & Clinical Leader in Advanced Muskuloskeletal bust some myths around acute back pain.  Thereafter, we will have some fun with a Christmas quiz, ECG and Xrays followed by another Classroom Simulation, an opportunity to work through a scenario in groups.  See you at Tute room 2, NCHER, 10:30AM.

Monday
Nov162015

Teaching 18 Nov

It's all about Breathing this week, with a focus on familiarizing ourselves with all things Non Invasive Ventilation. A core topic everyone must know, whatever stage of training you're at. Also, our last ED-ICU combined teaching for the year. Tute room 2, NCHER, 10:30am, see you there.

Friday
Nov062015

Teaching 11 Nov

Coming up next week will be Gastro Emergencies, brought to us by Dr Alvin Chung from 11am - 12pm and Airway skills session to finish.  There will also be an update on Registrar role in TNH SSU!  See you at tutorial room 2 at 1030h at NCHER.

Wednesday
Oct212015

Teaching 28 October

ITA 's will be conducted in the morning.  You know your timeslots.  Not a bad idea to bring along any supporting documents (certificates of courses or teaching attended, logbook, WBA etc) to supplement your assessment.

This will be followed by a compulsory O&G teaching session with Dr Paul Howat from 12:30 - 1:30pm, in the part task room.  There will be 2 Gynae simulation models for practice of speculum examination and other gynaecological procedures.  DO NOT MISS IT.